User-perceived latency is recognized as the central performance problem in the Web. We systematically measure factors contributing to this latency, across several locations. Our study reveals that domain name system (DNS) lookup times, transmission control protocol (TCP) connection-establishment, and start-of-session delays at hypertext transfer protocol (HTTP) servers are major causes of long waits. Moreover, wait, due to these factors also afflicts high-band- width users, which enjoy relatively short transmission times.
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